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Resolution dependence of magnetosheath waves in global hybrid-Vlasov simulations

Maxime Dubart1, Urs Ganse1, Adnane Osmane1, Andreas Johlander1, Markus Battarbee1, Maxime Grandin1, Yann Pfau-Kempf1, Lucile Turc1 and Minna Palmroth1,2

1Department of Physics, University of Helsinki, Helsinki, Finland2Space and Earth Observation Centre, Finnish Meteorological Institue, Helsinki, Finland

Simulations set-up- Global hybrid-Vlasov model: VLASIATOR [1]- Cartesian 2D spatial grid- Cartesian 3D velocity grid- Protons described as velocity distribution functions (VDFs)- Electrons as a cold massless charge neutralizing fluid- Closure of the system: generalised Ohm's law with Hall term

- Noon-midnight meridional plane (X-Z)- Inner boundary at 4.7 RE from the centre of the Earth- Solar wind: flowing in -X direction, 750 km/s- IMF: 5 nT, 45 degrees angle with respect to X, southward- Temperature: 0.5 MK- Density: 1 cm-3

Three different spatial resolutions𝚫r = 300 km = 0.76 di 𝚫r = 600 km = 0.38 di 𝚫r = 900 km = 0.25 di Ion-scale waves

Fast Fourier TransformMinimum variance analysis

Alfven Ion Cyclotron wavesMirror Modes [2]

Velocity Distribution Functions

[1] Palmroth, M. et al., Vlasov methods in space physics and astrophysics, LRCA, 4, https://doi.org/10.1007/s41115-018-0003-2, 2018[2] Hoilijoki, S. et al., Mirror modes in the Earth’s magnetosheath: Results from a global hybrid-Vlasov simulation, JGR, 121,https://doi.org/10.1002/2015JA022026, 2016. We acknowledge The European Research Council for Starting grant 200141-QuESpace, with which Vlasiator was developed, and Consolidator grant682068-PRESTISSIMO awarded to further develop Vlasiator and use it for scientific investigations. The Finnish Centre of Excellence in Research ofSustainable Space (FORESAIL), funded through the Academy of Finland grant number 312351, supports Vlasiator development and science as well. TheCSC – IT Center for Science in Finland is acknowledged for the Sisu and Taito supercomputer usage, which led to the results presented here. MaximeDubart thanks Thiago Brito for useful discussions throughout the study which helped carrying it out.

Annales Geophysicae Discussions, angeo-2020-24

Growth rate

Temperature anisotropy

Left-handed circularly polarised

- Proton cyclotron and Mirror

instabilities well resolved at

𝚫r = 300km. Sufficient maximum resolution

- Proton cyclotron instability not

resolved at𝚫r = 900km- Temperature

anisotropy increases at low resolution due to not resolving AIC

waves

- 𝚫r = 440km = 0.6 di presents an

acceptable minimum

resolution for study of

magnetosheath waves in global hybrid-Vlasov